Railway signaling systems



juh 3, 1956 H. A. THOMPSON RAILWAY SIGNALING SYSTEMS Filed Feb. l, 1952INVENTOR. Howavd A. T/zomfon.

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Lu L. Saut Hmmm!) RAHWAY SKGNALENG SYSTEMS Howard A. Thompson, Edgewood,Pa., assigner to Westinghouse Air Brake Company, Willmann-ng, Pa., ncorporation of Pennsylvania Application February 1, 1952, Serial No,269,475

3 Claims. (Cl. 21mm-d6) My invention relates to railway signalingsystems, and particularly to an improved form of railway signalingsystem in which the circuits employed for transmitting informationconcerning traic governing conditions in advance of a particularlocation may also be employed to ransmit information in the reversedirection.

in conventional railway signaling systems, a stretch of trailic to beprotected is divided into sections or blocks, each of which hasassociated therewith at the entrance end a signal for governingmovements of traffic into the block. Such signals may be governed by acombination of track circuits extending through the block to indicatethe traflic conditions within the immediate block in advance of asignal, and may also include a line circuit extending to the signallocation in advance which line circuit is arranged to reflect thetraffic conditions in the next block in advance of a particular waysidesignal. Thus when a train occupies the block immediately in advance of awayside signal, the shunting of the track circuit or track circuitswithin the block causes the signal to display its most restrictiveaspect, and when the train vacates the block immediately in advance ofthe signal, the track relays pick up to cause the signal to display acaution aspect. When the train vacates the second section in advance ofa signal, the line circuit is energized by energy governed over thetrack relays of the second block in advance so that a relay at the rstwayside signal is picked up, to cause the signal at that location todisplay a clear or proceed aspect'.

It may at times be desirable to transmit information over the linecircuits in the opposite direction to the usual direction of traffic` toprovide information at the end of a block concerning traffic conditionsat the entering end. One such application of an arrangement of this typeis employed in approach lighting signals in advance, by having a seriesrelay connected in the line circuit, so that when the tracl; relay ofthe block section is released the line circuit is interrupted and theseries approach relay releases its contact, thereby supplyinfy energy tothe lamp of the signal in advance of the approaching train. Anothercondition in which it is desirable to transmit traffic information fromthe entering end of the block section to the leaving end of the blocksection is the condition wherein vehicles which will not shunt the usualtrack circuits are operated over the stretch of railway track, and it isdesirable to provide a system for registering the entry and the exit ofthese vehicles in any particular block section. in this connection, itis also desirable to transmit supplemental information over the linecircuit from the exit end of the block to the entrance end of the blockto indicate that such registration has been accomplished.

Accordingly, it is an object of my invention to provide, in a railwaysignaling system of the type employing line wire control for signalsgoverning the movement of trallc in a particular' direction, means forutilizing the line circuit for transmitting additional information inthe direction opposite to the direction of traffic movement.

Another object of my invention is to provide a railway uit tates PatentO signaling system arranged to provide protection for nonshuntingvehicles traversing the section of track so equipped which will notinterfere with the normal operation of the signal system by trains orother shunting vehicles using the stretch.

Another object of my invention is to provide, in a system of the typedescribed, an arrangement whereby the entrance of a non-shunting vehicleinto the block section may be registered by suitable circuit means, andwhereby this registry will be indicated at the entrance point of thesection.

Another object of my invention is to provide, in a system of the typedescribed, a superimposed supplemental system for the protection ofnon-shouting vehicles, requiring the minimum of apparatus, and adaptedto be used with conventional signal systems.

Still another object of my invention is to provide, in a signalingsystem of the type described employing a pair of line wires for thecontrol of signal aspects in accordance with conditions in advance ofthe signals, means for at times recurrently interrupting the energyflowing in the line circuit, registering these interruptions at theenergized end of the line circuits, and indicating the reception andregistry of the impulses at the relay end of the line circuit.

@ther obiects of my invention and features of novelty thereof will beapparent from the following description taken in connection with theaccompanying drawing.

in practicing my invention, I provide, in a railway signaling system ofthe type employing a pair of line wires for governing the waysidesignals in accordance with conditions in advance of the signal, meansfor recurrently interrupting the line circuit at the receiving or relayend thereof, and means at the other end of the line circuit fordetecting the recurrent interruptions of the line circuit, in accordancewith a predetermined sequence or pattern of interruption. The receptionof the proper sequence or pattern of interruption causes theenergization of the line circuit to be changed in a characteristicmanner, and this change in the energization is reflected at thereceiving end of the line circuit, to thereby indicate that the controlinformation transmitted from the receiving end of the line circuit hasbeen received properly. in a preferred embodiment of my invention, lprovide means, such as a push button connected in series with the: linecircuit, at the entering end of a block section, for recurrentlyinterrupting the line circuit to thereby actuate a series con nectedrelay at the exit end of the block section. rThe recurrent operation ofthe series connected relay at the exit end of the block section causesthe operation of a counting chain, which counts and registers the numberof impulses transmitted by the opening and closing of the line circuit.lf the line circuit is recurrently opened and closed in the proper'sequence, as determined by the arrangement of the counting chain, arelay is energized to pole change the energy supplied to the linecircuit at the exit end of the block section, and thereby cause theoperation of a polarity responsive relay at the entering end of theblock section, to indicate that the desired conditions have beenobtained.

l shall describe one form of railway signaling system embodying myinvention, and shall then point out the novel features thereof inclaims.

The accompanying drawing is a diagrammatic View of a stretch of railwaytrack equipped with a railway signaling system constructed in accordancewith my invention, and which is arranged so that the apparatus normallyfunctions in the usual manner to govern the operation of trainproceeding through the stretch, but may be also employed to aifordprotection to the operators of vehicles which traverse the stretch andwhich are incapable of shunting the track circuit to cause the operationof the signaling system in its usual manner.

Referring to the drawing, there is shown a stretch of railway trackhaving track rails 1 and 3 which are divided into the customary blocksections by the conventional insulated joint 5. Only one complete blocksection, 2T, is shown in the drawing, together with portions ofadjoining block sections 1T and 3T, it being understood that theapparatus for each of the sections is arranged in a manner similar tothat shown for section 2T. Traic normally moves through the stretch inthe direction indicated by the arrow on the drawing, that is, from leftto right. At the entrance or left-hand end of each of the blocksections, there is located a wayside signal, such as signal 2S, whichfunctions to govern the entrance of traf into the section in advance ofthe signal. The signals may be of any of the well-known types, and ashere shown are of the conventional color light type, having a green lampG, a yellow lamp Y, and a red lamp R, which when lighted provide aproceed, caution and stop aspect, respectively. Additionally, at each ofthe signals there is provided an additional marker or auxiliary lampdesignated by the reference character M, for purposes which will besubsequently explained. Each of the sections in the stretch, such assection 2T, is equipped with a conventional direct current neutral trackcircuit comprising a track battery, such as battery ZTB connected acrossthe rails of the section at the exit end thereof, and a track relay,such as track relay ZTR, connected across the rails at the entrance endof the section. The track relays are shunted by the presence of a trainin the section and operate to govern the wayside signals thereby, aswill be explained in detail subsequently.

Between signal locations, such as signal 2S and signal 3S, there isprovided a pair of line wires, such as the wires designated by thereference characters 11 and 13, which are employed to additionallygovern the wayside signal at the entrance end of the section, and, inaccordance with my invention, to also provide means for providingprotection for non-shunting Vehicles Which are 0perated through thestretch.

Energy is supplied to the line circuit at the exit end of the blocksection, and energizes load devices such as polarity responsive relays2DR and ZMCR at the entrance end of the stretch, which also correspondsto the receiving end of the line circuit. The energy supplied to theline circuit at the transmitting end of the line, corresponding to theexit end of the stretch, also serves to energize a series relay such asrelay SAER. The relays 2DR and ZMCR are of the biased type, in which thecontacts of the relay are picked up when and only when energy issupplied through the winding of the relay in the direction indicated bythe arrow thereon. The load device which is normally energized by theenergy supplied over the line circuit, such as relay 2DR, functions as asignal control relay, and cooperates with the track relay, such as relayZTR, to govern theindication of the wayside sig nal. The other linecircuit load device, such as relay ZMCR, is normally supplied withenergy which is ineffective to pick up the contacts of the relay, butwhen the polarity of the line circuit is reversed, the second relaypicks up, and is used to indicate, at the receiving end of the linecircuit, the conditions at the transmitting end of the circuit. Theseries approach relay, such as the relay SAER, is connected in serieswith the circuit for supplying energy to the line wires, and thecircuits are arranged so that relay SAER is picked up at all timesexcept when the line circuit is interrupted, during which time the relaywill release its contacts.

In addition to the apparatus described above, there is located at eachsignal location, means for detecting and registering recurrent pick upand release of the series relay. This apparatus may be of any of thewell-known types for counting and registering impulses, such aswellknown electron tube circuits, but as here shown comprises a group ofcounting chain relays, such as relays 3A1, 3A2, 3A3, and 3A4, which arearranged so that the relays operate in sequence as a result of therecurrent operation of the contacts of series relay SAER, so that uponreception of the proper number of impulses, the counting chain relayswill become picked up to thereby cause the reversal of the polarity onthe line circuit to indicate at the receiving end of the line circuitthat a predetermined condition has been established at the transmittingend of the line circuit.

Energy for the operation of the various apparatus and the energizationof the signal lamps is provided by a suitable source or" low voltagedirect current, such as the battery LB, having its positive and negativeterminals designated by the reference characters B and N, respectively.

i'n addition to the apparatus described above, which is located at eachof the signal locations in the stretch, my invention also provides forthe inclusion of apparatus in the line circuit at intermediate points inthe stretch for the purpose of registering the entrance of a nonshuntingvehicle into the stretch at that point. This apparatus would comprise aseries push button such as the normally-closed push button ZPB- A, andan auxiliary indicator relay such as relay 2MCR-A, the push button andthe relay winding being connected in series with the line circuit at apredetermined point in the stretch. Relay ZMCR-A may indicate itsenergized condition by any suitable means, such as the lamp ZMKE-Aenergized by a battery ZMCB over a front contact a of relay 2MCR-A, whenthe relay is picked up, as shown in the drawing.

lt is believed that the description of the operation of the apparatusembodying my invention will be enhanced by describing the manner ofoperation of the equipment under various trac conditions.

In the normal condition of the apparatus as shown in the drawing, withno train occupying the stretch, and with no non-shunting vehicleregistered in the stretch, the line circuit extending between the signallocations 3S and 2S is energized by energy supplied from the battery atsignal location 3S, by a circuit which may be traced from terminal B,through the winding of series relay SAER, back contact a of relay SAS,the line wire l1, the normally closed contact of push button 2PB-A,front Contact a of relay ZTR (the track relay ZTR being picked up atthis time since the track section 2T is unoccupied), the normally-closedcontact of push button ZEPB, the winding of relay 2DR from left toright, the winding of relay ZMCR from left to right, the line wire 13including in series therewith the winding of relay 2MCR-A, back contactb of relay 3A4, back contact a of relay MCR, and front contact a ofrelay STR to terminal N. lt will be seen therefore, that at this time,with the apparatus in its normal condition, the energy supplied to theline circuit will cause the contact of the approach relay BAER f' to bepicked up, and the direction of flow of energy will be such that thecontacts of relay 2DR at signal location 2S will be picked up, while thecontacts of relay ZMCR and relay 2MCR-A will be released, the tlow ofcurrent through their windings being in the opposite direction to thatrequired to pick these relays up.

lt will now be assumed that a train proceeding through the stretchoccupies section 1T in the rear of signal 2S. Accordingly, at this timethe line circuit, not shown, cxtending rearwardly from signal 2S in themanner similar to that extending between signal 2S and signal 3S, willbe deenergized by the shunting of the track relay associated withsection 1T. Accordingly, the series relay ZAER vat signal 2S will becomedeenergized, audits back` Contact a will establish a circuit forlighting the green lamp G of signal 2S. This circuit may be traced fromterminal B at back contact a of relay ZAER, over back contact b of relayZMCR, front contact b of relay ZTR, front contact a of relay 2DR, andthrough the green lamp G of signal 2S to terminal N. Accordingly, thesignal 2S will display a clear or proceed aspect for the approachingtrain.

acarrear When the train moves into section 2T, the Wheels and axles ofthe train shunt the track circuit and relay 2TH accordingly releases andremains released as long as any portion of the section is occupied byany portion of the train. When contact b of relay ZTR releases, itinterrupts the circuit previously traced for supplying energy to thegreen lamp G of the signal and establishes a circuit, obvious on thedrawing, for supplying energy to the red lamp R of the signal.Additionally, when contact a of relay ZTR releases the liow of energy inthe line circuit previously described is interrupted, so that relays 2DRand 3AER are deenergized and these relays release. When contact a ofrelay 2DR releases, it further interrupts the circuit for supplyingenergy to the green lamp G of the signal, but at the present time, withcontact b of relay 2TR released, the release of contact a of relay 2DRhas no effect upon the signal indication, The release of relay BAER atsignal 3S will cause the lighting circuit for this signal to beestablished in the manner described above for signal 2S, so that signal3S will display a proceed aspect for the approaching train.Additionally, when contact a of relay SAER releases a circuit isestablished for supplying energy over the back contact of relay 3AER tothe winding of the first counting chain relay 3Al. Accordingly, relay3A1 picks up and its front contact a closes in a circuit for picking upthe second counting chain relay 3A2. However, the pick up circuit forcounting chain 3A2 is open at front contact a of approach relay `JAER,so that relay 3A2 does not pick up at this time.

When the train in question moves past signal 3S into section 3T, trackrelay 3T R will release and its front contact a will further interruptthe line circuit for conM tro-lling the relays 2DR and ZMCR at theentrance end of the section. 2T, relay ETR will again be energized andits contacts will pick up. When contact a of relay ZTR` picks up, itcloses the line circuit at the signal location 2S, but, as previouslyexplained, the circuit remains deenergized duc to the interruptionthereof by front contact a of the track relay STR. At this time, shoulda second train be following, a release of the series relay ZAER atsignal 2S will cause the signal to display a yellow or cautionindication, since at this time front contact b of relay ZTR will beclosed, but contact a of relay 2DR will be released so that a lightingcircuit for the yellow lamp Y of signal 2S will be completed upon thedeenergization of the series relay ZAER.

When the train vacates section 3T, track relay STR will be energized andits front contact a will again be closed, reestablishing the circuit forsupplying energy over the line wires to the relays 2DR and ZMCR atsignal location ZS. Since relay 3A4 remains released at this time, thepolarity of the energy supplied over the line wires to relays at signal2S is of the polarity to cause the contacts of the relay 2DR to pick up,and the contacts of the relay 2li/ICR will remain released. Accordingly,the signal lighting circuits for signal 2S are again connected in suchmanner that deenergization of the series relay ZAER by an approachingtrain will cause the signal 2S to display a green or clear aspect.

Reestablishment of the energy to the line circuit also causes thecontact a of relay BAER to become picked up. When contact a of relaySAER picks up, a circuit isestablished momentarily for the pick up ofrelay 3A?. which circuit includes front contact a of relay SAER andfront contact a of relay BA1. However, the supplyv of energy to relay3All is cut ott when contact a of relay 3AER picks up, so that thecontact a of relay 3A1 releases, after a short time interval, therebyinterrupting the supply of energy to the winding of relay 3A2, whichsubsequently releases. At this time7 relay SAS cannot pick up since whenrelay 3AER picks up its contact a, the pick up cirA cuit for relay SAS,which includes front contact a of relay SAZ and back contact a of relaySAER, is broken by con- When the rear of the train vacates section 6tact' a of relay SAER before front Contact a of relay SAE closes, sothat relay 3A3 remains released.

The apparatus is now restored to its normal position as shown on thedrawing. lt will be apparent from the foregoing description that theapparatus .normally functions in the usual manner of a two-blockthree-indication signaling system upon the passage of a train throughthe stretch equipped with this type of arrangement. The most restrictiveindication is controlled by the track relays, to denote occupancy orunoccupancy of the stretch immediately in advance of each Waysidesignal, while the line circuit described above provides an additionalcontrol for displaying a yellow or green` aspect in accordance with theoccupancy or nonoccupancy of the second section ahead of the waysidesignal, provided of course, that the first section is unoccupied. asdetermined by the track circuit of that section.

It will now be assumed that the operator ot a motor car or other vehiclewhich is not capable of shunting the track circuit desires to place thevehicle upon the rails at the entrance end of one of the sections andproceed therethrough. To establish the necessary protection for themotor car, it is necessary that its presence within a given stretch beregistered and that a distinctive indicao tion is provided to warn theenginernen of approaching trains of the fact that a motor car has beenregistered into the section.

To register a motor car in the section from the entrance end thereof,such as at signal 2S, the motor car operator will operate the pushbutton ZEPB twice in succession, with the intervals between operationsrela tively short. As will be apparent from the previous dis-- cussionot the line circuit, each operation of the push button ZEPB causes theline circuit to become deenergized and results in the release of therelay 3AER at the exit end of the section for such time as the pushbutton ZEPB is depressed.

When the motor car operator depressies the push button ZEPB twice at theentering end of the section 2T, the contact a of relay SAER at the exitend of the section will be released, picked up, released, and thenpicked up again. Upon the rst release of contact a of relay SAER energyis supplied to the winding of the tirst conne ing chain relay 3Al, sothat this relay picks up. When the contact a of relay SAER picks up forthe first time, a circuit is established over front contact a of relayAlit and front contact a of relay 3A1 to cause the pick up of the secondcounting chain relay 3A2. When contact a of relay SAER releases inresponse to the second operation of push button ZEPB, energy is suppliedto the third counting chain relay 3A3 by a circuit including backcontact a of relay SAER and front contact a of relay 3A3. When thecontact a of relay SAER is finally picked up after the push button ZEPBis released the second and last time, a circuit is established includingfront contact a of relay SAER and front Contact a of relay 3A3 to pickup the fourth counting chain relay 3A4l. When relay 3Ad picks up, astick circuit is established for the relay` which circuit may be tracedfrom terminal B, over a normally closed push button SXPB, back contact bot relay SAS, back contact b of relay SMCR, front contact c of relay3A4', and through the winding of relay 3A4 to terminal N. Accordingly,at this time relay 3A@ will have its contact picked up and will remainpicked up after the previous counting chain relays have released, as aresult of the closure of the stick circuit of the relay. When contacts aand b of relay 3AflV pick up, the supply of energy to the line circuitis pole changed, so that energy is now supplied to the relays at theentrance end of the section by a circuit which may be traced fromterminal B through the winding of series relay 3AER, over front contactb of relay 3A4, line wire 13 including in series therewith the windingof relay 2MCR--A, the winding of relay ZMCR, the winding of relay 2DR,all from right to left, over the contact ofV push button ZEPB,

front contact a of track relay 2TR, line wire 11 including in seriestherewith the contact of the push button ZPB-A, and over front contact aof relay 3Ali to terminal N. The ilow of current in the circuit at thistime is such as to cause the contacts of relays ZMCR and 2MCR-A to pickup, and the contacts of relay 2DR will be released and remain released.

The picking up of relay ZMCR at the entrance end of the section causesan indication lamp ZMKE to be supplied with energy by a circuitincluding front Contact a of relay ZMCR, to thereby indicate to theoperator of the motor car that the registry of the entrance of the motorcar in the section 2T has been properly accomplished. Additionally, whenContact b of relay ZMCR picks up it establishes a circuit for supplyingenergy to the marker lamp M of signal 2S, in the event that lthe seriesrelayl ZAER should be released by the approach of a train. Accordingly,if the train is approaching section iT at this time, the lamp M ofsignal 2S will be lighted, to

thereby provide a distinctive aspect from signal 2S, in-

dicating to the engineman of the approaching train that a motor car hasbeen registered in the section in advance, so that the engineman maygovern the operation of his train accordingly.

lt will now be apparent that the purpose of the push button ZPB- A andthe series relay ZMCR-A connected in the line wires in the middle of theblock section is for the purpose of permitting the motor car operator toregister the entry of his car in case the car is placed upon the tracksat the middle block section. Additionally, the relay ZMCR-A provides anindication at that point as to whether or not a motor car is registeredin the block by controlling the indicator light MKB-A. it will beapparent that a plurality or" push buttons and indication relays may beconnected in series in the line circuit at various places throughout theblock section, wherever it may be desired to provide for registrationand/or indication of the registration of the motor cars in the blocksection.

When the motor car reaches the exit end of section 2T, the countingchain relay 3A4 may be released to clear out the registration by eitherone of two means. First, the operator may push the cancellation buttonSXBP, which will break the stick circuit for the relay SAA, or, second,if the motor car is to progress into section 3T, the operation of thepush button for registering the car in section 3T will cause relay SMCRto pick up, in the manner similar to that described .for relay MCR, andwhen relay 3MCR picks up, its back contact b Will interrupt the stickcircuit for relay 3A4. ln either case, the release of relay 3A@ causesits contacts a and b to pole change the energy supplied to the linecircuit, with the result that the motor car indication relays 2MCR andMCR-A will be released, and relay 2DR will be en ergized as previouslydescribed. Such operation will restore the apparatus to its normalcondition as shown in the drawing and described heretofore.

It will be noted that when relay SMCR is picked up, its front contact ainserts a resistance R1 in the circuit tor supplying energy to the linecircuit and the relays ZDR and ZMCR at the entrance end of the blocksection. This resistance is proportioned so that the current which owsthrough the line circuit at this time will be insufficient to pick uprelay 2DR but will be suflicient to cause relay SAER to'remainenergized. Accordingly, when relay SMCR is picked up by the registry ofa motor car in section 3T, signal 3S will display the distinctiveindication consisting of the lighted marker lamp M upon the approach ofa train, and additionally, the signal in the rear of the section inwhich the motor car is registered, in this case signal 2S, cannotdisplay better than a yellow aspect, thus warning the engineman of anapproaching train that a restrictive condition exists in advance.However, since the relay BAER remains energized at this time it ispossible for a second motor car operator 8 to register his car insection 2T, by operation of the push button ZEPB, to thereby operaterelay BAER in the manner described above to pick up the counting chainrelay and register the motor car in section ZT.

The system also functions to register the entry of a motor car andprovide cancellation of this registry when the motor car backs out ofthe section at the same end Where it was originally registered into thesection. For example, let it be assumed that a motor car operator hasregistered in section 2T by operation of push button ZEPB at signal 2S,in the manner described above. It will now be assumed that the motor caroperator wishes to reverse his direction of travel and back out ofsection 2T, removing the car from the rails at signal location 2S. Afterthe car is removed from the rails, the motor car operator depresses thepush button ZEPB twice in succession, holding the push button depressedfor a relatively long interval during the second operation thereor".When the push button is iirst depressed, relay SAER. will release andits back contact a will establish a pick up circuit for relay 3A1. Whenrelay SAER picks up at the end of the rst operation of the push buttonZEPB, the circuit for picking up relay 3A2 is established over frontcontact a of relay SAER and front contact a of relay 3A1. When relay3AER is released upon the second operation of push button ZEPB, relay3A3 is picked up over back contact a of relay SAER and front contact aof relay 3A2. The previously traced stick circuit for relay 3A4 isinterrupted by the opening of back Contact b of relay 3A3, and since thepickup circuit for relay 3A4 is open at this time due to the release ofrelay SAER, the supply of energy is cut off from relay 3A4, and after ashort time interval, relay 3A4 releases, restoring the polarity of theline circuit to normal. Since contact a of relay BAER will remainreleased for a considerable interval at this time, relay 3A2 willrelease during this interval, thereby opening the circuit for relay 3A3,which in turn releases, so that when relay SAER is finally picked upupon the second release of the push button, the circuit for picking uprelay 3A4 will not be established, since relay SAS will be released andits front contact a will hold the pick up circuit for relay 3A4- open.

From the foregoing it will be seen that the arrangement of the circuitsas shown in the drawing and embodying my invention provides for theoperation of nonshunting vehicles through a stretch of track equippedwith a signaling system which operates in the conventional manner fortrains and motor vehicles which are capable of shunting the trackcircuits. Such operation is accomplished by providing means forrecurrently interrupting a normally energized line circuit at thereceiving end thereof in a predetermined sequence, registering theinterruptions at the transmitting end thereof, and providing anindication at the receiving end of the line circuit that the registryhas been accomplished by changing the characteristics of the energysupplied over the line circuit.

Although I have herein shown and described only one form of railwaysignaling system embodying my invention, it will be apparent to thoseskilled in the art that various changes and modications may be madetherein within the scope of the appended claims without departing fromthe spirit and scope of my invention.

Having thus described my invention, what I claim is:

l. In combination, a source of electrical energy, a load device, a pairof conductors for supplying energy from said source to said load device,said load device being connected to said pair of conductors at one endthereof and said source being connected to said conductors at the otherend thereof, means connected between said load device and one of saidconductors for at times recurrently interrupting the connections of saidload device to said source in a predetermined sequence, detecting meansconnected to said conductors at the end of said conductors at which saidsource is located and respongrsser 9, sive to changes in the interruptedenergy supplied from said source to said conductors, relay meansgoverned by said detecting means and rendered effective when and onlywhen said detecting means is recurrently operated in said predeterminedsequence, said rel'ay means operative when rendered effective to changethe character of the energy supplied from said source to saidconductors, and means associated with said load device for indicatingthe character of the energy supplied over said conductors to said loaddevice.

2. ln combination, a source of electrical energy, a load device, a pairot conductors for supplying energy from said source to said load device,means associated with said load device for at times" recurrentlyinterrupting the connection of saidload device to said conductors in apredetermined sequence, a series relay connected between said source andsaid conductors and having contacts which are picked up or releasedaccording as energy is or is not being supplied to said load device fromsaid source, counting chain relay means governed by said series relaycontacts and rendered effective when and only when said series relaycontacts are picked up and released in said predetermined sequence, andmeans governed by said counting chain relay means for changing thecharacteristics of the energy supplied to said load device from saidsource when said counting chain relay means is rendered effective.

3. ln combination, a section of railway track over which traiic normallymoves in a given direction from a designated entrance end of the stretchto the designated exit end of the stretch, a pair of conductorsextending from the entrance end of the stretch to the exit end of thestretch, means for normally supplying direct current energy of a givenpolarity to said conductors at the exit end of said stretch inaccordance with trai-lic conditions in advance of said stretch, awayside signal located at the entrance end of said stretch, a signalcontrol relay connected to said conductors at the entrance end of saidstretch and responsive to energy of said given polarity for governingsaid wayside signal, a circuit-interrupting Contact at the entrance endof the Stretch and effective at times for interrupting said line circuitin a predetermined sequence, registry means including a relay countingchain located at the exit end of said stretch and rendered effectivewhen said line circuit is interrupted in said predetermined sequence forreversing the polarity of the energy supplied to said line circuit fromsaid source, and auxiliary relay means associated with said signalcontrol relay for indicating the reversal of the polarity of energysupplied to said line circuit.

4. ln combination, a section of railway track over which traiiicnormally moves in a given direction from a designated entrance end ofthe stretch to the designated exit end of the stretch, a pair ofconductors extending from the entrance end of the stretch to the eXitend of the stretch` means for normally supplying direct current energyof a given polarity to said conductors at the exit end ot said stretchin accordance with tratlic conditions in advance ot said stretch, awayside signal located at the entrance end ot` said stretch, a signalcontrol relay connected to said conductors at the entrance end of saidstretch and responsive to energy of said given polarity for governingsaid wayside signal, a circuit interrupting Contact at the entrance endof the stretch and eiective at times lor interrupting said line circuitin a predetermined sequence, registry means including a relay countingchain located at the exit end of said stretch and rendered eliectivewhen said line circuit is interrupted in said predetermined sequence forreversing the polarity of the energy supplied to said line circuit fromsaid source, auxiliary relay means associated with said signal controlrelay and responsive to reversal of the polarity oi the energy suppliedto said line circuit, and circuit means governed by said auxiliary relaymeans ior causing said wayside signal to display a distinctive aspect,

itl"

5. A railway signal system comprising a stretch of track divided intosections, a track circuit including la track relay for each section, apair of line conductors for each section, at least one of which includesin series therewith a front contact of the associated track relay,energy supply means for each section for supplying the pair olfconductors for the section next in the rear with energy of a givenpolarity in accordance with traiiic conditions in advance, a signalcontrol relay for each section receiving energy from said conductors andresponsive only to energy or" said given polarity, a signal for eachsection governed jointly by said track relay and said signal control`relay, circuit controlling means located at each of said signallocations for at times interrupting said line conductors in apredetermined sequence, a series relay at each signal, location andconnected in series with the line conductors for the section in therear, a group oli` counting relays governed by said series relay, saidcounting relays being rendered operative when and only when said lineconductors are interrupted in said sequence, pole-changing meansgoverned by said counting relays andV effective when rendered operativeto reverse the polarity of the energy supplied to said line conductors,an auxiliary control relay for each section receiving energy from saidconductors and responsive only to energy of reverse polarity, andindication means governed by said auxiliary relay.

6. A railway signal system comprising a stretch of track divided intosections, a track circuit including a track relay for each section, apair of line conductors for each section, at least one of which includesin series therewith a front contact of the associated track relay,energy supply means for each section for supplying the pair ofconductors for the section next in the rear with energy of a givenpolarity in accordance with traliic conditions in advance, a signalcontrol relay for each section receiving energy from said conductors andresponsive only to energy of said given polarity, a signal for eachsection governed jointly by said track relay and said signal controlrelay, circuit controlling means located at each of said signallocations for at times interrupting said line conductors in apredetermined sequence, a series relay at each signal location andconnected in series with the line conductors for the section in therear, a group of counting relays governed by said series relay, saidcounting relays being rendered operative when and only when said lineconductors are interrupted in said sequence, pole-changing meansgoverned by said counting relays and elifective when rendered operativeto reverse the polarity of the energy supplied to said line conductors,an auxiliary control relay for each section receiving energy from saidconductors and responsive only to energy of reverse polarity, and meansgoverned by said auxiliary relay for causing said signal to display adistinctive aspect.

7. A railway signal system comprising a stretch of track divided intosections, a track circuit including a track relay for each section, apair of line conductors for each section, at least one of which includesin series therewith a front contact of the associated track relay, asource of direct current energy for each section for supplying energy tothe pair of conductors for the adjacent section in the rear, apole-changing relay having contacts which govern the polarity of theenergy supplied to said conductors from said source, polarized relaymeans receiving energy from said conductors, circuit controlling meansfor at times interrupting the ow of' energy in said conductors, a seriesrelay having a winding connected in series between said source and saidcontacts of the polechanging relay, said series relay having contactswhich are picked up or released according as energy is or is not flowingthrough said conductors, a signal for said section, said signal beinggoverned jointly by said track relay and said polarized relay meansenergized with energy of a given polarity, a chain of counting relaysgoverned by said series relay and arranged so that the counting relaysvare picked up sequentially when said line conductors are interrupted insaid predetermined sequence, a pick-up circuit for said pole-changingrelay including contacts of said series relay and the last relay in saidcounting chain, a stick circuit for said pole-changing relay including anormally closed circuit controller, and indication means including saidpolarized relay means for indicating the reversal of polarity of theenergy supplied to said line conductors.

8. A railway signal system comprising a stretch of track divided intosections, a track circuit including a track relay for each section, apair of line conductors for each section, at least one of which includesin series therewith a front contact of the associated track relay, asource of direct current energy for each section for supplying energy tothe pair of conductors for the adjacent section in the rear, apole-changing relay having contacts which govern the polarity of theenergy supplied to said conductors from said source, polarized relaymeans receiving energy from said conductors, circuit controlling meansfor at times interrupting the flow of energy in said conductors, aseries relay having a winding connected in series between said sourceand said contacts of the polechanging relay, said series relay havingcontacts which are picked up or released according as energy is or isnot flowing through said conductors, a signal for said section, saidsignal being governed jointly by said track relay and said polarizedrelay means energized with energy of a given polarity, a chain ofcounting relays governed by said series relay and arranged so that thecounting relays are picked up sequentially when said line conductors areinterrupted in said predetermined sequence, a pick-up circuit for saidpole-changing relay including contacts of said series relay and the lastrelay in said counting chain, a stick circuit for said pole-changingrelay including a normally closed circuit controller, and means governedby said polarized relay means for causing said signal to display a disftinctive aspect when the polarity of the energy supplied over said linecircuit is reversed.

References Cited in the tile of this patent UNITED STATES PATENTS2,168,817 Ptlasterer Aug. 8, 1939 2,232,379 Field c Feb. 18, 19412,503,716 Failor Apr. 11, 1950 2,572,234 Young Oct. 25, 1951

